Environmental factors such as microbiota or infection trigger immune-mediated tissue injury, which leads to chronic mucosal diseases in the genetically susceptible subjects, such as Inflammatory Bowel Diseases (IBD). Stem cell therapy has recently achieved many successful cases in the personalized treatment of IBD, but intestinal epithelial stem cell (IESC) treatment is still at an early stage. JAK-STAT activation wa suggested to promote adult intestinal stem cell division and differentiation, respectively, and thereby could drive the renewal of intestinal epithelial cells (IEC). We recently reported that STAT5 signaling prevents intestinal barrier dysfunction and promotes mucosal healing in colitic mouse models. Furthermore, our preliminary data indicated that deletion of STAT5 decreased the expression of stem cell markers Lgr5, Ascl2, and Olfm4, and inhibited NOTCH activation and cellular junction maturation in adult IESC-derived organoid. We therefore hypothesize that STAT5 signaling controls adult IESC activity via regulation of a stem cell gene signature to promote intercellular junction formation; activation of STAT5 signaling enhances IEC organoid engraftment against infection-induced intestinal barrier dysfunction. We will test our hypotheses with the following two Aims. Our Aim 1 will determine the role of STAT5 signaling for adult IESC differentiation. The studies in this Aim will, first, inducibly delete IEC STAT5 or hyperactivate IEC STAT5 in mice to characterize IESC homeostasis, stem cell gene profiles, and Wnt/Notch signaling in adult mouse intestines. Second, using human pluripotent stem cells-derived intestinal organoids, we will genetically manipulate STAT5 expression to define STAT5's role in the regulation of Wnt/Notch signaling during IESC differentiation. Our Aim 2 will define the requirement of STAT5 signaling for differentiation-associated development of IEC monolayers. First, we will characterize tight junction development using both STAT5 deficient and STAT5 inducible IESC-derived organoids. Second, we will culture these mouse organoids to implant the recipient control mice to assess IESC integrity and tight junction formation. Overall, we will determine that epithelial STAT5 regulates a stem cell gene signature via interplay with NOTCH signaling to promote intercellular junction reformation for healing mucosal inflammation. Our studies will demonstrate an essential role for STAT5 in the regulation of adult stem cell homeostasis via a stem cell gene signature, and will explore a novel engineered tissue therapy that directly heals the epithelial barrier disruption during mucosal inflammation. We propose a paradigm shift for this research field from understanding STAT5 signaling as an essential regulator of stem cell biology toward developing the potential therapeutic tool. We believe this exploratory R21 mechanism will permit a collaborative team of basic scientists and clinical investigators to start a brand-new project, and explore a novel potential therapeutic avenue for restoring epithelial barrier dysfunction in mucosal inflammation.